This research will investigate the manner in which Mexican immigrants to the United States and the descendants of Mexican immigrants adapt their fertility to the experience of living in a country characterized by substantially lower fertility than their country of origin. Two aspects of this adjustment will be examined. The first concerns the possibility that the population of Mexican descent will decrease its fertility depending on length of time spent in the host society. That is, it is hypothesized that fertility will vary inversely with generation. The second concerns the possibility that fertility differentials by socioeconomic status will be greater among higher than lower generation Mexican Americans owing to a greater tendency for "minority group status" to depress the fertility of higher than lower generation couples. That is, it is hypothesized that "minority group status" effects on fertility will be more characteristic of later generation Mexican Americans than on recent immigrants. The first hypothesis will be tested using data for a Mexican American sample (self-identified as being of Mexican origin) drawn from the 1970 1/100 fifteen percent Public Use Sample tapes for the United States. The second will be tested using data for the Mexican American sample viewed in comparison with data for an Anglo sample (white, not of Mexican or other Spanish descent) drawn from the same source.